Dynamically adjustable reference line sampling point density for autonomous vehicles

ABSTRACT

According to some embodiments, a system receives a first set of reference points based on a map and a route information, the first plurality of reference points representing a reference line in which the ADV is to follow. The system selects a second set of reference points along the reference line, including iteratively performing, selecting a current reference point from the first set of reference points, determining a sampling distance along the first set of reference points based on the currently selected reference point using a nonlinear algorithm, and selecting a next reference point based on the determined sampling distance such that a density of the second set of reference points closer to the ADV is higher than a density of the selected reference points farther away from the ADV. The system plans a trajectory for the ADV using the second set of reference points to control the ADV.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to operating autonomous vehicles. More particularly, embodiments of the disclosure relate to dynamically adjusted reference line sampling point density for autonomous driving vehicles (ADVs).

BACKGROUND

Vehicles operating in an autonomous mode (e.g., driverless) can relieve occupants, especially the driver, from some driving-related responsibilities. When operating in an autonomous mode, the vehicle can navigate to various locations using onboard sensors, allowing the vehicle to travel with minimal human interaction or in some cases without any passengers.

Vehicles can operate in an autonomous mode by a planned driving trajectory. A planned driving trajectory is generated by an ADV's planning module relying on “reference lines”. A reference line is a smooth line on a geometric word map. Reference lines are represented by a set of points along a road curve. A typical 200 meter road curve uses 1000 points for a reference line. The computation time for many algorithms, such as reference line projections and driving trajectory decision and planning, are directly related to the number of points or density of a reference line.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure are illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements.

FIG. 1 is a block diagram illustrating a networked system according to one embodiment.

FIG. 2 is a block diagram illustrating an example of a sensor and control system using by an autonomous vehicle according to one embodiment.

FIGS. 3A-3B are block diagrams illustrating examples of a perception and planning system used by an autonomous vehicle according to some embodiments.

FIG. 4 is a block diagram illustrating an example reference line points with equidistance.

FIG. 5 is a block diagram illustrating an example dynamically adjusted reference line sampling point density according to one embodiment.

FIG. 6 is a flow diagram illustrating a method according to one embodiment.

FIG. 7 is a block diagram illustrating a data processing system according to one embodiment.

DETAILED DESCRIPTION

Various embodiments and aspects of the disclosures will be described with reference to details discussed below, and the accompanying drawings will illustrate the various embodiments. The following description and drawings are illustrative of the disclosure and are not to be construed as limiting the disclosure. Numerous specific details are described to provide a thorough understanding of various embodiments of the present disclosure. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of embodiments of the present disclosures.

Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in conjunction with the embodiment can be included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification do not necessarily all refer to the same embodiment.

According to some embodiments, a system dynamically adjusts a reference line sampling point density. In one embodiment, the system receives a first set of reference points based on a map and a route information, the first plurality of reference points representing a reference line in which the ADV is to follow. The system selects a second set of reference points along the reference line, including iteratively performing, selecting a current reference point from the first set of reference points, determining a sampling distance along the first set of reference points based on the currently selected reference point using a nonlinear algorithm, and selecting a next reference point based on the determined sampling distance such that a density of the second set of reference points closer to the ADV is higher than a density of the selected reference points farther away from the ADV. The system plans a trajectory for the ADV using the second set of reference points to control the ADV.

FIG. 1 is a block diagram illustrating an autonomous vehicle network configuration according to one embodiment of the disclosure. Referring to FIG. 1, network configuration 100 includes autonomous vehicle 101 that may be communicatively coupled to one or more servers 103-104 over a network 102. Although there is one autonomous vehicle shown, multiple autonomous vehicles can be coupled to each other and/or coupled to servers 103-104 over network 102. Network 102 may be any type of networks such as a local area network (LAN), a wide area network (WAN) such as the Internet, a cellular network, a satellite network, or a combination thereof, wired or wireless. Server(s) 103-104 may be any kind of servers or a cluster of servers, such as Web or cloud servers, application servers, backend servers, or a combination thereof. Servers 103-104 may be data analytics servers, content servers, traffic information servers, map and point of interest (MPOI) severs, or location servers, etc.

An autonomous vehicle refers to a vehicle that can be configured to in an autonomous mode in which the vehicle navigates through an environment with little or no input from a driver. Such an autonomous vehicle can include a sensor system having one or more sensors that are configured to detect information about the environment in which the vehicle operates. The vehicle and its associated controller(s) use the detected information to navigate through the environment. Autonomous vehicle 101 can operate in a manual mode, a full autonomous mode, or a partial autonomous mode.

In one embodiment, autonomous vehicle 101 includes, but is not limited to, perception and planning system 110, vehicle control system 111, wireless communication system 112, user interface system 113, and sensor system 115. Autonomous vehicle 101 may further include certain common components included in ordinary vehicles, such as, an engine, wheels, steering wheel, transmission, etc., which may be controlled by vehicle control system 111 and/or perception and planning system 110 using a variety of communication signals and/or commands, such as, for example, acceleration signals or commands, deceleration signals or commands, steering signals or commands, braking signals or commands, etc.

Components 110-115 may be communicatively coupled to each other via an interconnect, a bus, a network, or a combination thereof. For example, components 110-115 may be communicatively coupled to each other via a controller area network (CAN) bus. A CAN bus is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other in applications without a host computer. It is a message-based protocol, designed originally for multiplex electrical wiring within automobiles, but is also used in many other contexts.

Referring now to FIG. 2, in one embodiment, sensor system 115 includes, but it is not limited to, one or more cameras 211, global positioning system (GPS) unit 212, inertial measurement unit (IMU) 213, radar unit 214, and a light detection and range (LIDAR) unit 215. GPS system 212 may include a transceiver operable to provide information regarding the position of the autonomous vehicle. IMU unit 213 may sense position and orientation changes of the autonomous vehicle based on inertial acceleration. Radar unit 214 may represent a system that utilizes radio signals to sense objects within the local environment of the autonomous vehicle. In some embodiments, in addition to sensing objects, radar unit 214 may additionally sense the speed and/or heading of the objects. LIDAR unit 215 may sense objects in the environment in which the autonomous vehicle is located using lasers. LIDAR unit 215 could include one or more laser sources, a laser scanner, and one or more detectors, among other system components. Cameras 211 may include one or more devices to capture images of the environment surrounding the autonomous vehicle. Cameras 211 may be still cameras and/or video cameras. A camera may be mechanically movable, for example, by mounting the camera on a rotating and/or tilting a platform.

Sensor system 115 may further include other sensors, such as, a sonar sensor, an infrared sensor, a steering sensor, a throttle sensor, a braking sensor, and an audio sensor (e.g., microphone). An audio sensor may be configured to capture sound from the environment surrounding the autonomous vehicle. A steering sensor may be configured to sense the steering angle of a steering wheel, wheels of the vehicle, or a combination thereof. A throttle sensor and a braking sensor sense the throttle position and braking position of the vehicle, respectively. In some situations, a throttle sensor and a braking sensor may be integrated as an integrated throttle/braking sensor.

In one embodiment, vehicle control system 111 includes, but is not limited to, steering unit 201, throttle unit 202 (also referred to as an acceleration unit), and braking unit 203. Steering unit 201 is to adjust the direction or heading of the vehicle. Throttle unit 202 is to control the speed of the motor or engine that in turn control the speed and acceleration of the vehicle. Braking unit 203 is to decelerate the vehicle by providing friction to slow the wheels or tires of the vehicle. Note that the components as shown in FIG. 2 may be implemented in hardware, software, or a combination thereof.

Referring back to FIG. 1, wireless communication system 112 is to allow communication between autonomous vehicle 101 and external systems, such as devices, sensors, other vehicles, etc. For example, wireless communication system 112 can wirelessly communicate with one or more devices directly or via a communication network, such as servers 103-104 over network 102. Wireless communication system 112 can use any cellular communication network or a wireless local area network (WLAN), e.g., using WiFi to communicate with another component or system. Wireless communication system 112 could communicate directly with a device (e.g., a mobile device of a passenger, a display device, a speaker within vehicle 101), for example, using an infrared link, Bluetooth, etc. User interface system 113 may be part of peripheral devices implemented within vehicle 101 including, for example, a keyword, a touch screen display device, a microphone, and a speaker, etc.

Some or all of the functions of autonomous vehicle 101 may be controlled or managed by perception and planning system 110, especially when operating in an autonomous driving mode. Perception and planning system 110 includes the necessary hardware (e.g., processor(s), memory, storage) and software (e.g., operating system, planning and routing programs) to receive information from sensor system 115, control system 111, wireless communication system 112, and/or user interface system 113, process the received information, plan a route or path from a starting point to a destination point, and then drive vehicle 101 based on the planning and control information. Alternatively, perception and planning system 110 may be integrated with vehicle control system 111.

For example, a user as a passenger may specify a starting location and a destination of a trip, for example, via a user interface. Perception and planning system 110 obtains the trip related data. For example, perception and planning system 110 may obtain location and route information from an MPOI server, which may be a part of servers 103-104. The location server provides location services and the MPOI server provides map services and the POIs of certain locations. Alternatively, such location and MPOI information may be cached locally in a persistent storage device of perception and planning system 110.

While autonomous vehicle 101 is moving along the route, perception and planning system 110 may also obtain real-time traffic information from a traffic information system or server (TIS). Note that servers 103-104 may be operated by a third party entity. Alternatively, the functionalities of servers 103-104 may be integrated with perception and planning system 110. Based on the real-time traffic information, MPOI information, and location information, as well as real-time local environment data detected or sensed by sensor system 115 (e.g., obstacles, objects, nearby vehicles), perception and planning system 110 can plan an optimal route and drive vehicle 101, for example, via control system 111, according to the planned route to reach the specified destination safely and efficiently.

Server 103 may be a data analytics system to perform data analytics services for a variety of clients. In one embodiment, data analytics system 103 includes data collector 121 and machine learning engine 122. Data collector 121 collects driving statistics 123 from a variety of vehicles, either autonomous vehicles or regular vehicles driven by human drivers. Driving statistics 123 include information indicating the driving commands (e.g., throttle, brake, steering commands) issued and responses of the vehicles (e.g., speeds, accelerations, decelerations, directions) captured by sensors of the vehicles at different points in time. Driving statistics 123 may further include information describing the driving environments at different points in time, such as, for example, routes (including starting and destination locations), MPOIs, road conditions, weather conditions, etc.

Based on driving statistics 123, machine learning engine 122 generates or trains a set of rules, algorithms, and/or models 124 for a variety of purposes. In one embodiment, for example, algorithms/model 124 may include a sampling model or algorithm that can dynamically adjust a reference line sampling point density. The sampling model can include minimum sampling distances, maximum sampling distances, and one or more sampling algorithms to modify a reference line sampling point density. The sampling model can be uploaded onto the autonomous driving vehicle to be used to dynamically adjust a reference line point density of a reference line at real time.

FIGS. 3A and 3B are block diagrams illustrating an example of a perception and planning system used with an autonomous vehicle according to one embodiment. System 300 may be implemented as a part of autonomous vehicle 101 of FIG. 1 including, but is not limited to, perception and planning system 110, control system 111, and sensor system 115. Referring to FIGS. 3A-3B, perception and planning system 110 includes, but is not limited to, localization module 301, perception module 302, prediction module 303, decision module 304, planning module 305, control module 306, routing/sampling module 307, and reference line generator 309.

Some or all of modules 301-309 may be implemented in software, hardware, or a combination thereof. For example, these modules may be installed in persistent storage device 352, loaded into memory 351, and executed by one or more processors (not shown). Note that some or all of these modules may be communicatively coupled to or integrated with some or all modules of vehicle control system 111 of FIG. 2. Some of modules 301-309 may be integrated together as an integrated module. For example, routing/sampling module 307 and reference line generator 309 may be integrated as a single module.

Localization module 301 determines a current location of autonomous vehicle 300 (e.g., leveraging GPS unit 212) and manages any data related to a trip or route of a user. Localization module 301 (also referred to as a map and route module) manages any data related to a trip or route of a user. A user may log in and specify a starting location and a destination of a trip, for example, via a user interface. Localization module 301 communicates with other components of autonomous vehicle 300, such as map and route information 311, to obtain the trip related data. For example, localization module 301 may obtain location and route information from a location server and a map and POI (MPOI) server. A location server provides location services and an MPOI server provides map services and the POIs of certain locations, which may be cached as part of map and route information 311. While autonomous vehicle 300 is moving along the route, localization module 301 may also obtain real-time traffic information from a traffic information system or server.

Based on the sensor data provided by sensor system 115 and localization information obtained by localization module 301, a perception of the surrounding environment is determined by perception module 302. The perception information may represent what an ordinary driver would perceive surrounding a vehicle in which the driver is driving. The perception can include the lane configuration (e.g., straight or curve lanes), traffic light signals, a relative position of another vehicle, a pedestrian, a building, crosswalk, or other traffic related signs (e.g., stop signs, yield signs), etc., for example, in a form of an object.

Perception module 302 may include a computer vision system or functionalities of a computer vision system to process and analyze images captured by one or more cameras in order to identify objects and/or features in the environment of autonomous vehicle. The objects can include traffic signals, road way boundaries, other vehicles, pedestrians, and/or obstacles, etc. The computer vision system may use an object recognition algorithm, video tracking, and other computer vision techniques. In some embodiments, the computer vision system can map an environment, track objects, and estimate the speed of objects, etc. Perception module 302 can also detect objects based on other sensors data provided by other sensors such as a radar and/or LIDAR.

For each of the objects, prediction module 303 predicts how the object will behave under the circumstances. The prediction is performed based on the perception data perceiving the driving environment at the point in time in view of a set of map/rout information 311 and traffic rules 312. For example, if the object is a vehicle at an opposing direction and the current driving environment includes an intersection, prediction module 303 will predict whether the vehicle will likely move straight forward or make a turn. If the perception data indicates that the intersection has no traffic light, prediction module 303 may predict that the vehicle may have to fully stop prior to enter the intersection. If the perception data indicates that the vehicle is currently at a left-turn only lane or a right-turn only lane, prediction module 303 may predict that the vehicle will more likely make a left turn or right turn respectively.

For each of the objects, decision module 304 makes a decision regarding how to handle the object. For example, for a particular object (e.g., another vehicle in a crossing route) as well as its metadata describing the object (e.g., a speed, direction, turning angle), decision module 304 decides how to encounter the object (e.g., overtake, yield, stop, pass). Decision module 304 may make such decisions according to a set of rules such as traffic rules or driving rules 312, which may be stored in persistent storage device 352.

Based on a decision for each of the objects perceived, planning module 305 plans a path or route for the autonomous vehicle, as well as driving parameters (e.g., distance, speed, and/or turning angle). That is, for a given object, decision module 304 decides what to do with the object, while planning module 305 determines how to do it. For example, for a given object, decision module 304 may decide to pass the object, while planning module 305 may determine whether to pass on the left side or right side of the object. Planning and control data is generated by planning module 305 including information describing how vehicle 300 would move in a next moving cycle (e.g., next route/path segment). For example, the planning and control data may instruct vehicle 300 to move 10 meters at a speed of 30 mile per hour (mph), then change to a right lane at the speed of 25 mph.

Based on the planning and control data, control module 306 controls and drives the autonomous vehicle, by sending proper commands or signals to vehicle control system 111, according to a route or path defined by the planning and control data. The planning and control data include sufficient information to drive the vehicle from a first point to a second point of a route or path using appropriate vehicle settings or driving parameters (e.g., throttle, braking, and turning commands) at different points in time along the path or route.

In one embodiment, the planning phase is performed in a number of planning cycles, also referred to as command cycles, such as, for example, in every time interval of 100 milliseconds (ms). For each of the planning cycles or command cycles, one or more control commands will be issued based on the planning and control data. That is, for every 100 ms, planning module 305 plans a next route segment or path segment, for example, including a target position and the time required for the ADV to reach the target position. Alternatively, planning module 305 may further specify the specific speed, direction, and/or steering angle, etc. In one embodiment, planning module 305 plans a route segment or path segment for the next predetermined period of time such as 5 seconds. For each planning cycle, planning module 305 plans a target position for the current cycle (e.g., next 5 seconds) based on a target position planned in a previous cycle. Control module 306 then generates one or more control commands (e.g., throttle, brake, steering control commands) based on the planning and control data of the current cycle.

Note that decision module 304 and planning module 305 may be integrated as an integrated module. Decision module 304/planning module 305 may include a navigation system or functionalities of a navigation system to determine a driving path for the autonomous vehicle. For example, the navigation system may determine a series of speeds and directional headings to effect movement of the autonomous vehicle along a path that substantially avoids perceived obstacles while generally advancing the autonomous vehicle along a roadway-based path leading to an ultimate destination. The destination may be set according to user inputs via user interface system 113. The navigation system may update the driving path dynamically while the autonomous vehicle is in operation. The navigation system can incorporate data from a GPS system and one or more maps so as to determine the driving path for the autonomous vehicle.

Decision module 304/planning module 305 may further include a collision avoidance system or functionalities of a collision avoidance system to identify, evaluate, and avoid or otherwise negotiate potential obstacles in the environment of the autonomous vehicle. For example, the collision avoidance system may effect changes in the navigation of the autonomous vehicle by operating one or more subsystems in control system 111 to undertake swerving maneuvers, turning maneuvers, braking maneuvers, etc. The collision avoidance system may automatically determine feasible obstacle avoidance maneuvers on the basis of surrounding traffic patterns, road conditions, etc. The collision avoidance system may be configured such that a swerving maneuver is not undertaken when other sensor systems detect vehicles, construction barriers, etc. in the region adjacent the autonomous vehicle that would be swerved into. The collision avoidance system may automatically select the maneuver that is both available and maximizes safety of occupants of the autonomous vehicle. The collision avoidance system may select an avoidance maneuver predicted to cause the least amount of acceleration in a passenger cabin of the autonomous vehicle.

Routing module 307 can generate reference lines, for example, from map information such as information of road segments, vehicular lanes of road segments, and distances from lanes to curb. For example, a road can be divided into sections or segments {A, B, and C} to denote three road segments. Three lanes of road segment A can be enumerated {A1, A2, and A3}. A reference line is generated by generating reference points of uniform density along the reference line. For example, for a vehicular lane, routing module 307 can connect midpoints of two opposing curbs or extremities of the vehicular lane provided by a map data. Based on the midpoints and machine learning data representing collected data points of vehicles previously driven on the vehicular lane at different points in time, routing module 307 can calculate the reference points by selecting a subset of the collected data points within a predetermined proximity of the vehicular lane and applying a smoothing function to the midpoints in view of the subset of collected data points.

Based on reference points, reference line generator 309 may generate a reference line by interpolating the reference points such that the generated reference line is used as a reference line for controlling ADVs on the vehicular lane. In some embodiments, a reference points table and a road segments table representing the reference lines are downloaded in real-time to ADVs such that the ADVs can generate reference lines from the reference points table and the road segments table based on the ADVs' geographical location and driving direction. For example, in one embodiment, an ADV can generate a reference line by requesting routing service for a path segment by a path segment identifier representing an upcoming road section ahead and/or based on the ADV's GPS location. Based on a path segment identifier, a routing service can return to the ADV reference points table containing reference points for all lanes of road segments of interest. ADV can look up reference points for a lane for a path segment to generate a reference line for controlling the ADV on the vehicular lane.

In one embodiment, to reduce a computational load of the ADV, sampling module 307 can determine a minimum sampling distance and a maximum sampling distance for a length of road to dynamically adjust a density of the generated reference line for a reference line with a non-uniform line density. For example, sampling module 307 can apply a sampling algorithm (as part of sampling algorithm/model 313) to dynamically adjust a density of the generated reference line to reduce the number of reference points of the reference line based on availability of computational resources or to satisfy some objective requirements. For example, sampling module 307 may receive a request from perception and planning system 110 (by way of settings change via a user interface, or an update downloaded to the ADV via server 104) to reduce a reference point density by about five fold without a change to the reference line point density near the ADV.

Sampling module 307 may dynamically adjust the reference line point density by adjusting a maximum sampling distance and calculating a new reference line point density by trial and error until the sampling module 307 reaches the computational objective requirements. In one scenario, sampling module 307 performs a sampling algorithm calculation having inputs of minimum sampling distance, maximum sampling distance, and sampling length. Sampling module 307 may try a maximum sampling distance of 0.9, 1.0, 1.1, 1.2, etc. meters, while keeping constant a minimum sampling distance of 0.2 meters (e.g., ensuring a reference line point density near the ADV is about 0.2 meters/point) and a road length of 200 meters, to acquire a new reference line with point density having a five-fold reduction. The newly acquired maximum sampling distance then can be used to generate subsequent non-uniform reference line points, accordingly.

As described above, route or routing module 307 manages any data related to a trip or route of a user. The user of the ADV specifies a starting and a destination location to obtain trip related data. Trip related data includes route segments and a reference line or reference points of the route segment. For example, based on route map info 311, route module 307 generates a route or road segments table and a reference points table. The reference points are in relations to road segments and/or lanes in the road segments table. The reference points can be interpolated to form one or more reference lines to control the ADV. The reference points can be specific to road segments and/or specific lanes of road segments.

For example, a road segments table can be a name-value pair to include previous and next road lanes for road segments A-D. E.g., a road segments table may be: {(A1, B1), (B1, C1), (C1, D1)} for road segments A-D having lane 1. A reference points table may include reference points in x-y coordinates for road segments lanes, e.g., {(A1, (x1, y1)), (B1, (x2, y2)), (C1, (x3, y3)), (D1, (x4, y4))}, where A1 . . . D1 refers to lane 1 of road segments A-D, and (x1, y1) . . . (x4, y4) are corresponding real world coordinates. In one embodiment, road segments and/or lanes are divided into a predetermined length such as approximately 200 meters segments/lanes. In another embodiment, road segments and/or lanes are divided into variable length segments/lanes depending on road conditions such as road curvatures. In some embodiments, each road segment and/or lane can include several reference points. In some embodiments, reference points can be converted to other coordinate systems, e.g., latitude-longitude. Sampling module 307 can then dynamically adjust a density of the reference points.

Note that some or all of the components as shown and described above may be implemented in software, hardware, or a combination thereof. For example, such components can be implemented as software installed and stored in a persistent storage device, which can be loaded and executed in a memory by a processor (not shown) to carry out the processes or operations described throughout this application. Alternatively, such components can be implemented as executable code programmed or embedded into dedicated hardware such as an integrated circuit (e.g., an application specific IC or ASIC), a digital signal processor (DSP), or a field programmable gate array (FPGA), which can be accessed via a corresponding driver and/or operating system from an application. Furthermore, such components can be implemented as specific hardware logic in a processor or processor core as part of an instruction set accessible by a software component via one or more specific instructions.

FIG. 4 is a block diagram illustrating an example reference line points before a sampling algorithm/model is applied. Referring to FIG. 4, reference line 401 represents a set of reference points 402 starting from ADV 101. Reference points 402 may be provided by routing module 407 based on a current location of the ADV and a destination location to be reached. Reference points 402 (e.g., a first set of reference points) may be in an (x, y) real world coordinate system or a longitudinal-latitudinal coordinate system. In one example, reference points 402 (from initial point 403 to end point 404) can have points approximately 0.2 meters apart representing reference line 401 of length 200 meters.

FIG. 5 is a block diagram illustrating an example dynamically adjusted reference line sampling point density according to one embodiment. In one embodiment, referring to FIG. 5, reference line 401 includes reference points 403, 502-506 (e.g., a second set of reference points) with a non-uniform density. Reference points 502-506 can be selected along reference line 401 by sampling module 307 using a sampling algorithm/model (as part of sampling algorithm/model 313). A sample algorithm can calculate a non-uniform density of reference point provided: a minimum sample point distance, a maximum sample point distance, and a length of the reference line. In one embodiment, the sampling algorithm is:

${{f(s)} = \frac{A}{1 + e^{{Bs} + C}}};{A = {Dmax}};{C = {\log \left( \frac{A}{{Dmin} - 1} \right)}};$ ${B = {\left( {{\log \left( \frac{A}{\left( {A - \sigma} \right) - 1} \right)} - C} \right)\text{/}L}},$

where s is a distance from the ADV of a current sampling reference point along the first set of reference points, Dmax is a maximum sampling point distance, Dmin is a minimum sampling point distance, L is a length of the reference line, and σ is a small number such as 1e-3.

Referring to FIG. 5, for the purpose of illustration, reference line 401 can include reference points 403, 502-506 with a non-uniform density. Reference points 502-506 can be selected along reference line 401 or its corresponding reference points by sampling module 307. In one embodiment, sampling module 307 starts at initial point 403 (e.g., s=0) and apply a sampling algorithm at the initial point s=0 to calculate a sampling point distance f(s) 514, at s=0. Sampling module 307 then selects the next sampling point 503 which is sampling point distance 514 away from point 403. Sampling module 307 applies the sampling algorithm at point 503 to calculate sampling point distance 515 to select point 504. Sampling module 307 applies the sampling algorithm to subsequent sampling points (504 . . . 506) to calculate subsequent sampling point distances to select subsequent sampling points until the sampling algorithm reaches an end point, such as point 506. This way a reference line with a non-uniform density of reference points (e.g., points 403, 502-506) can be utilized subsequently by other modules, such as decision and planning modules 304-305, to plan a driving trajectory to control ADV 101. The motivation of controlling a density of the reference points is to be able to reduce a computational time of many algorithms, such as algorithms in prediction, decision, and planning cycles, which are linearly related to the number of points on a reference line. A reference line with fewer reference points can lead to more efficient and faster cycles. However, reducing the number of reference points or increasing the sampling intervals between reference points (especially closer to the ADV) may introduce errors such as errors in not being able to accurately capture events occurring between adjacent reference points that could otherwise be captured. Thus, diminishing the density of the reference points as distance gets farther away from the ADV would not introduce such errors near the immediate driving range of the ADV while at the same time would allow a performance gain in computational efficiency as distance is farther away from the ADV.

Since the reference points located farther away from the vehicle, it is unlikely those reference points will be utilized to control the ADV in a current cycle. When a next planning cycle comes, a new reference line is generated and the previous reference line of the previous planning cycle may not be utilized. Thus, by sampling the reference points near the vehicle at a higher density level we can ensure the trajectory will be generated accurately. By sampling the reference points farther away from the ADV at a lower density level, which are unlikely used to control the ADV in the current planning cycle, we can reduce the computation time.

FIG. 6 is a flow diagram illustrating a method to control an ADV according to one embodiment. Processing 600 may be performed by processing logic which may include software, hardware, or a combination thereof. For example, process 600 may be performed by sampling module 307 of FIGS. 3A-3B. Referring to FIG. 6, at block 601, processing logic receives a first set of reference points based on a map and a route information, the first set of reference points representing a reference line in which the ADV is to follow. At block 602, processing logic selects a second set of reference points along the reference line corresponding to the first set of reference points, including iteratively performing, at block 603, selecting a current reference point from the first set of reference points. At block 604, determining a sampling distance along the first set of reference points based on the currently selected reference point using a nonlinear algorithm. At block 605, selecting a next reference point along the first set of reference points based on the determined sampling distance such that a density of the second set of reference points close to the ADV is higher than a density of the selected reference points farther away from the ADV. At block 606, processing logic plans a trajectory for the ADV using the second set of reference points to control the ADV.

In one embodiment, determining a sampling distance further includes determining a minimum sampling distance and determining a maximum sampling distance, where the sampling distance is determined based on the minimum sampling distance and the maximum sampling distance. In another embodiment, the sampling distance is determined further in view of a length of the reference line.

In one embodiment, the second set of reference points includes points that are separated by a distance approximately equal to the minimum sampling distances near the ADV and a distance approximately equal to the maximum sampling distances away from the ADV. In one embodiment, the second set of reference points has a density that gradually decreases away from the ADV.

In one embodiment, the nonlinear algorithm is an inverse of an exponential function. In one embodiment, the nonlinear algorithm is

$\frac{A}{1 + e^{{Bx} + C}},$

where A is a maximum sampling distance, C is a logarithmic of A divided by a minimum sampling distance minus one, B is a logarithmic of (A/A−σ)−1, minus C, divided by a length of the reference line, and σ is a fractional number.

FIG. 7 is a block diagram illustrating an example of a data processing system which may be used with one embodiment of the disclosure. For example, system 1500 may represent any of data processing systems described above performing any of the processes or methods described above, such as, for example, perception and planning system 110 or servers 103-104 of FIG. 1. System 1500 can include many different components. These components can be implemented as integrated circuits (ICs), portions thereof, discrete electronic devices, or other modules adapted to a circuit board such as a motherboard or add-in card of the computer system, or as components otherwise incorporated within a chassis of the computer system.

Note also that system 1500 is intended to show a high level view of many components of the computer system. However, it is to be understood that additional components may be present in certain implementations and furthermore, different arrangement of the components shown may occur in other implementations. System 1500 may represent a desktop, a laptop, a tablet, a server, a mobile phone, a media player, a personal digital assistant (PDA), a Smartwatch, a personal communicator, a gaming device, a network router or hub, a wireless access point (AP) or repeater, a set-top box, or a combination thereof. Further, while only a single machine or system is illustrated, the term “machine” or “system” shall also be taken to include any collection of machines or systems that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein.

In one embodiment, system 1500 includes processor 1501, memory 1503, and devices 1505-1508 connected via a bus or an interconnect 1510. Processor 1501 may represent a single processor or multiple processors with a single processor core or multiple processor cores included therein. Processor 1501 may represent one or more general-purpose processors such as a microprocessor, a central processing unit (CPU), or the like. More particularly, processor 1501 may be a complex instruction set computing (CISC) microprocessor, reduced instruction set computing (RISC) microprocessor, very long instruction word (VLIW) microprocessor, or processor implementing other instruction sets, or processors implementing a combination of instruction sets. Processor 1501 may also be one or more special-purpose processors such as an application specific integrated circuit (ASIC), a cellular or baseband processor, a field programmable gate array (FPGA), a digital signal processor (DSP), a network processor, a graphics processor, a communications processor, a cryptographic processor, a co-processor, an embedded processor, or any other type of logic capable of processing instructions.

Processor 1501, which may be a low power multi-core processor socket such as an ultra-low voltage processor, may act as a main processing unit and central hub for communication with the various components of the system. Such processor can be implemented as a system on chip (SoC). Processor 1501 is configured to execute instructions for performing the operations and steps discussed herein. System 1500 may further include a graphics interface that communicates with optional graphics subsystem 1504, which may include a display controller, a graphics processor, and/or a display device.

Processor 1501 may communicate with memory 1503, which in one embodiment can be implemented via multiple memory devices to provide for a given amount of system memory. Memory 1503 may include one or more volatile storage (or memory) devices such as random access memory (RAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), static RAM (SRAM), or other types of storage devices. Memory 1503 may store information including sequences of instructions that are executed by processor 1501, or any other device. For example, executable code and/or data of a variety of operating systems, device drivers, firmware (e.g., input output basic system or BIOS), and/or applications can be loaded in memory 1503 and executed by processor 1501. An operating system can be any kind of operating systems, such as, for example, Robot Operating System (ROS), Windows® operating system from Microsoft®, Mac OS/iOS from Apple, Android® from Google®, LINUX, UNIX, or other real-time or embedded operating systems.

System 1500 may further include IO devices such as devices 1505-1508, including network interface device(s) 1505, optional input device(s) 1506, and other optional IO device(s) 1507. Network interface device 1505 may include a wireless transceiver and/or a network interface card (NIC). The wireless transceiver may be a WiFi transceiver, an infrared transceiver, a Bluetooth transceiver, a WiMax transceiver, a wireless cellular telephony transceiver, a satellite transceiver (e.g., a global positioning system (GPS) transceiver), or other radio frequency (RF) transceivers, or a combination thereof. The NIC may be an Ethernet card.

Input device(s) 1506 may include a mouse, a touch pad, a touch sensitive screen (which may be integrated with display device 1504), a pointer device such as a stylus, and/or a keyboard (e.g., physical keyboard or a virtual keyboard displayed as part of a touch sensitive screen). For example, input device 1506 may include a touch screen controller coupled to a touch screen. The touch screen and touch screen controller can, for example, detect contact and movement or break thereof using any of a plurality of touch sensitivity technologies, including but not limited to capacitive, resistive, infrared, and surface acoustic wave technologies, as well as other proximity sensor arrays or other elements for determining one or more points of contact with the touch screen.

IO devices 1507 may include an audio device. An audio device may include a speaker and/or a microphone to facilitate voice-enabled functions, such as voice recognition, voice replication, digital recording, and/or telephony functions. Other IO devices 1507 may further include universal serial bus (USB) port(s), parallel port(s), serial port(s), a printer, a network interface, a bus bridge (e.g., a PCI-PCI bridge), sensor(s) (e.g., a motion sensor such as an accelerometer, gyroscope, a magnetometer, a light sensor, compass, a proximity sensor, etc.), or a combination thereof. Devices 1507 may further include an imaging processing subsystem (e.g., a camera), which may include an optical sensor, such as a charged coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) optical sensor, utilized to facilitate camera functions, such as recording photographs and video clips. Certain sensors may be coupled to interconnect 1510 via a sensor hub (not shown), while other devices such as a keyboard or thermal sensor may be controlled by an embedded controller (not shown), dependent upon the specific configuration or design of system 1500.

To provide for persistent storage of information such as data, applications, one or more operating systems and so forth, a mass storage (not shown) may also couple to processor 1501. In various embodiments, to enable a thinner and lighter system design as well as to improve system responsiveness, this mass storage may be implemented via a solid state device (SSD). However in other embodiments, the mass storage may primarily be implemented using a hard disk drive (HDD) with a smaller amount of SSD storage to act as a SSD cache to enable non-volatile storage of context state and other such information during power down events so that a fast power up can occur on re-initiation of system activities. Also a flash device may be coupled to processor 1501, e.g., via a serial peripheral interface (SPI). This flash device may provide for non-volatile storage of system software, including BIOS as well as other firmware of the system.

Storage device 1508 may include computer-accessible storage medium 1509 (also known as a machine-readable storage medium or a computer-readable medium) on which is stored one or more sets of instructions or software (e.g., module, unit, and/or logic 1528) embodying any one or more of the methodologies or functions described herein. Processing module/unit/logic 1528 may represent any of the components described above, such as, for example, routing/sampling module 307 of FIG. 3. Processing module/unit/logic 1528 may also reside, completely or at least partially, within memory 1503 and/or within processor 1501 during execution thereof by data processing system 1500, memory 1503 and processor 1501 also constituting machine-accessible storage media. Processing module/unit/logic 1528 may further be transmitted or received over a network via network interface device 1505.

Computer-readable storage medium 1509 may also be used to store the some software functionalities described above persistently. While computer-readable storage medium 1509 is shown in an exemplary embodiment to be a single medium, the term “computer-readable storage medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions. The terms “computer-readable storage medium” shall also be taken to include any medium that is capable of storing or encoding a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the present disclosure. The term “computer-readable storage medium” shall accordingly be taken to include, but not be limited to, solid-state memories, and optical and magnetic media, or any other non-transitory machine-readable medium.

Processing module/unit/logic 1528, components and other features described herein can be implemented as discrete hardware components or integrated in the functionality of hardware components such as ASICS, FPGAs, DSPs or similar devices. In addition, processing module/unit/logic 1528 can be implemented as firmware or functional circuitry within hardware devices. Further, processing module/unit/logic 1528 can be implemented in any combination hardware devices and software components.

Note that while system 1500 is illustrated with various components of a data processing system, it is not intended to represent any particular architecture or manner of interconnecting the components; as such details are not germane to embodiments of the present disclosure. It will also be appreciated that network computers, handheld computers, mobile phones, servers, and/or other data processing systems which have fewer components or perhaps more components may also be used with embodiments of the disclosure.

Some portions of the preceding detailed descriptions have been presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the ways used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities.

It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the above discussion, it is appreciated that throughout the description, discussions utilizing terms such as those set forth in the claims below, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

Embodiments of the disclosure also relate to an apparatus for performing the operations herein. Such a computer program is stored in a non-transitory computer readable medium. A machine-readable medium includes any mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., a computer) readable storage medium (e.g., read only memory (“ROM”), random access memory (“RAM”), magnetic disk storage media, optical storage media, flash memory devices).

The processes or methods depicted in the preceding figures may be performed by processing logic that comprises hardware (e.g. circuitry, dedicated logic, etc.), software (e.g., embodied on a non-transitory computer readable medium), or a combination of both. Although the processes or methods are described above in terms of some sequential operations, it should be appreciated that some of the operations described may be performed in a different order. Moreover, some operations may be performed in parallel rather than sequentially.

Embodiments of the present disclosure are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of embodiments of the disclosure as described herein.

In the foregoing specification, embodiments of the disclosure have been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the disclosure as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. 

1. A computer-implemented method to generate a driving trajectory with progressive sampling distance for an autonomous driving vehicle (ADV), the method comprising: receiving a first set of reference points based on a map and a route information, the first set of reference points representing a reference line in which the ADV is to follow; selecting a second set of reference points along the reference line corresponding to the first set of reference points, including iteratively performing, selecting a current reference point from the first set of reference points; determining a sampling distance along the first set of reference points based on the currently selected reference point using a nonlinear algorithm; and selecting a next reference point along the first set of reference points based on the determined sampling distance such that a density of the selected reference points closer to the ADV is higher than a density of the selected reference points farther away from the ADV; and planning a trajectory for the ADV using the second set of reference points to control the ADV.
 2. The computer-implemented method of claim 1, wherein determining a sampling distance further comprises: determining a minimum sampling distance; and determining a maximum sampling distance, wherein the sampling distance is determined based on the minimum sampling distance and the maximum sampling distance.
 3. The computer-implemented method of claim 2, wherein the sampling distance is determined further in view of a length of the reference line.
 4. The computer-implemented method of claim 1, wherein the second set of reference points includes points that are separated by a distance approximately equal to the minimum sampling distances near the ADV and a distance approximately equal to the maximum sampling distances away from the ADV.
 5. The computer-implemented method of claim 1, wherein the second set of reference points has a density that gradually decreases away from the ADV.
 6. The computer-implemented method of claim 1, wherein the nonlinear algorithm is an inverse of an exponential function.
 7. The computer-implemented method of claim 1, wherein the nonlinear algorithm is ${{f(s)} = \frac{A}{1 + e^{{Bs} + C}}},$ wherein s is a distance away from the ADV, A is a maximum sampling distance, C is a logarithmic of A divided by a minimum sampling distance minus one, and B is a logarithmic of A/((A−σ)−1), minus C, divided by a length of the reference line, wherein σ is a fractional number.
 8. A non-transitory machine-readable medium having instructions stored therein, which when executed by a processor, cause the processor to perform operations, the operations comprising: receiving a first set of reference points based on a map and a route information, the first set of reference points representing a reference line in which the ADV is to follow; selecting a second set of reference points along the reference line corresponding to the first set of reference points, including iteratively performing, selecting a current reference point from the first set of reference points; determining a sampling distance along the first set of reference points based on the currently selected reference point using a nonlinear algorithm; and selecting a next reference point along the first set of reference points based on the determined sampling distance such that a density of the selected reference points closer to the ADV is higher than a density of the selected reference points farther away from the ADV; and planning a trajectory for the ADV using the second set of reference points to control the ADV.
 9. The non-transitory machine-readable medium of claim 8, wherein determining a sampling distance further comprises: determining a minimum sampling distance; and determining a maximum sampling distance, wherein the sampling distance is determined based on the minimum sampling distance and the maximum sampling distance.
 10. The non-transitory machine-readable medium of claim 9, wherein the sampling distance is determined further in view of a length of the reference line.
 11. The non-transitory machine-readable medium of claim 8, wherein the second set of reference points includes points that are separated by a distance approximately equal to the minimum sampling distances near the ADV and a distance approximately equal to the maximum sampling distances away from the ADV.
 12. The non-transitory machine-readable medium of claim 8, wherein the second set of reference points has a density that gradually decreases away from the ADV.
 13. The non-transitory machine-readable medium of claim 8, wherein the nonlinear algorithm is an inverse of an exponential function.
 14. The non-transitory machine-readable medium of claim 8, wherein the nonlinear algorithm is ${{f(s)} = \frac{A}{1 + e^{{Bs} + C}}},$ wherein s is a distance away from the ADV, A is a maximum sampling distance, C is a logarithmic of A divided by a minimum sampling distance minus one, and B is a logarithmic of A/((A−σ)−1), minus C, divided by a length of the reference line, wherein σ is a fractional number.
 15. A data processing system, comprising: one or more processors; and a memory coupled to the one or more processors to store instructions, which when executed by the one or more processors, cause the processor to perform operations, the operations including receiving a first set of reference points based on a map and a route information, the first set of reference points representing a reference line in which the ADV is to follow; selecting a second set of reference points along the reference line corresponding to the first set of reference points, including iteratively performing, selecting a current reference point from the first set of reference points; determining a sampling distance along the first set of reference points based on the currently selected reference point using a nonlinear algorithm; and selecting a next reference point along the first set of reference points based on the determined sampling distance such that a density of the selected reference points closer to the ADV is higher than a density of the selected reference points farther away from the ADV; and planning a trajectory for the ADV using the second set of reference points to control the ADV.
 16. The system of claim 15, wherein determining a sampling distance further comprises: determining a minimum sampling distance; and determining a maximum sampling distance, wherein the sampling distance is determined based on the minimum sampling distance and the maximum sampling distance.
 17. The system of claim 16, wherein the sampling distance is determined further in view of a length of the reference line.
 18. The system of claim 15, wherein the second set of reference points includes points that are separated by a distance approximately equal to the minimum sampling distances near the ADV and a distance approximately equal to the maximum sampling distances away from the ADV.
 19. The system of claim 15, wherein the second set of reference points has a density that gradually decreases away from the ADV.
 20. The system of claim 15, wherein the nonlinear algorithm is an inverse of an exponential function.
 21. The system of claim 15, wherein the nonlinear algorithm is ${{f(s)} = \frac{A}{1 + e^{{Bs} + C}}},$ wherein s is a distance away from the ADV, A is a maximum sampling distance, C is a logarithmic of A divided by a minimum sampling distance minus one, and B is a logarithmic of A/((A−σ)−1), minus C, divided by a length of the reference line, wherein σ is a fractional number. 